Conventional anchors include a Japanese anchor, in which bills (d) are formed in ends of arms (c) extending to opposite sides of a crown (b) formed at the extreme end of a shank (a), and a stock (e) perpendicular to the arms (c) is provided on the crown (b), as shown in FIGS. 6 to 8; a Western anchor, in which a stock (g) perpendicular to arms (f) is provided on a shank (h), as shown in FIGS. 9 to 11; a warship anchor, in which a rotatable bill shaft (j) is provided at the extreme end of a shank (i) so that the bill shaft (j) is perpendicular to and to be projected on opposite sides of the shank (i), a bill seat plate (1) having a window hole (k) in a central portion thereof is provided with both sides in a vertical central portion of the seat plate (1) secured to both sides of the bill shaft (j), and bills (m) perpendicular to the seat plate (1) are secured to the plate (1), as shown in FIGS. 12 to 14; and a Danforth anchor, in which a rotatable bill shaft (p) is provided at the extreme end of a shank (n) so that the bill shaft (p) is perpendicular to and to be projected on opposite sides of the shank (n), and two bills (q) which is triangular and of which extreme ends are close to each other are secured to opposite ends of a bill shaft (p), as shown in FIGS. 15-17.
Both the Japanese anchor and Western anchor have substantially the same shape and same performance. The shank is square or round in section and has a large area in contact with the ground and will not move into the sediment at the bottom of the water but only the bill enters the sediment at the bottom of the water. Therefore, an anchoring force is relatively small.
In the warship anchor, the shank is square in section to hold the weight and has a large area in contact with the ground and will not move into the sediment at the bottom of the water. In addition, the bill seat plate receives a resistance of the sediment and the force acts in a direction of floating the bill. Therefore, an anchoring force is also relatively small.
The Danforth anchor is provided with two bills which have a triangular shape which may easily enter the sediment at the bottom of the water. However, the extreme ends of the bills are close to each other, and therefore, in case where the sediment layer at the bottom of the water is hard or in case where seaweed is present at the bottom of the water, the bills are hard to move into the bottom of the water and tend to turn over. There involves a problem in that anchorage is not reliable.
In view of the foregoing, the present inventor has proposed an anchor as disclosed in a Japanese Patent Laid-Open Publication No. 110591/1985 which comprises two bills (s) having a larger surface area to strengthen the anchoring force, bill stopping frames (t) and a thin and wider shank (u) to facilitate the movement thereof into the sediment at the bottom of the water, as shown in FIGS. 18 to 20.
Furthermore, an anchor disclosed in a Japanese Patent Laid-Open Publication No. 69895/1976 comprises a shank, two bills pivoted to said shank and having a delta shape, a trimming plate or a head surface disposed on either bill, said trimming plate having a width narrower than the entire width of the bill. This is an anchor for anchoring a ship for particular purposes, a dredger, an offshore platform for boring, and the like, in which both outer ends of both the trimming plates are connected to the outer edges of the bills by means of stabilizing plates which close and form an acute angle by the direction of the shank and the surface of the bills.
In this anchor, the outer ends of both trimming plates are connected outer ends of triangular bills through stabilizing plates to thereby increase a stability of the anchor, which eliminates the need of a stock provided in a conventional Danforce type anchor, removing various problems such as an increase in width of the anchor because of the stock, a damage to the hull because of the stock, twining of a steel wire to the stock, etc. However, since the weight of a portion comprising the trimming plates frontwardly of a pivot pin, stabilizing plates and front portions of the triangular bills is substantially the same as the weight of a portion comprising rear portions of the triangular bills at the rear of the pivot pin, the triangular bills make a landing on the bottom in a substantially horizontal state. Therefore, the extreme ends of the triangular bills are hard to pierce into the bottom of the water. In case where the earth of the bottom of the water is hard, even if the anchor is pulled by an anchored object, the extreme ends of the triangular bills will not be pierced into the bottom of the water but possibly floated. Moreover, since the extreme ends of the left and right triangular bills are converged on the side of the shank, the extreme ends of the triangular bills are pierced into substantially the same place of the bottom of the water and moved therein. Therefore, the anchoring force of the anchor is small and is not sufficient in stability. When a lateral force acts on the shank due to the movement of an anchored object or a steel wire because of wind or waves, the anchor having been moved into the bottom of the water is possibly disengaged and turned over.
An anchor disclosed in a Japanese Patent Laid-Open Publication No 146392/1979 comprises a hook having two hook members, a shank hinged to said hook and a rear stabilizer, in which the shank is mounted between hook members to a hinge pin which is located substantially at the center of gravity of the entire construction of the hook by means of face plates which are interconnected at inner ends by means of flange plates and converged in a mutual direction from said inner ends to form a thin extreme end, a rear portion and a side end. The anchor further comprises a head plate mounted on the hook on each side of the hinge pin to limit a rotational angle of the hook and a blade plate towards the rear stabilizer located at the side corner of the hook from the head plate.
According to this anchor, two hook members of a closed hollow construction formed by the flange plate and two face plates are connected at inner ends by means of the flange plate and the head plate and the stabilizer located at the side corner of the hook are connected by the blade plate to thereby enhance the strength of the hook and increase the stability of the anchor. However, since the weight of a portion comprising the head plate frontwardly of the hinge pin, the blade plate, the stabilizer and the front portion of the hook member is substantially the same as the weight of a portion comprising the rear portion of the hook member at the rear of the hinge pin and since the finger-like extreme ends of the left and right hook members are converged on the shank side, the finger-like extreme ends of the hook members are hard to be pierced into the bottom of the water, the anchoring force of the anchor is small and the stability is not sufficient.
In the anchor according to the present invention, when making a landing on the bottom of the water, three parts, i.e., left and right bills and a lower auxiliary bill encroach the bottom of the water. Therefore, the anchorage is positive. In addition, the shank as well as the bill stopping frame are made thin in wall thickness, and therefore, the entire anchor encroaches the sediment of the bottom of the water, providing a great anchoring force.
Since the bill is wide and of the spread-open type, the anchor is prevented from being turned over. The inside of the bill stopping frame has a space, and therefore, the sediment can pass therethrough, minimizing the resistance of the sediment in the bottom of the water with respect to the encroachment. The anchorage of the anchor is quick and positive.
Since the shank, bills and bill stopping frame are thin, the anchor of the present invention is lighter than the conventional anchors, and the work and labor during casting an anchor can be relieved.